Instead of "telling" him what the proper ruling should have been, I would've asked the same questions we ask
those partners we get assigned with from time to time.
So how long have you been officiating?
Really
How did you get started?
Cool, I got started by...
How far do you want to go with this?
NOTE: MAY BE THE LAST QUESTION YOU NEED TO ASK DEPENDING UPON THIS ANSWER
What levels of ball do you work?
Really... you should join the HS association, we need more guys like you 
What camps will you be attending this summer?
Yes, camps... that's one of the keys to us getting better at the craft.
I don't play anymore but since I work wreck, church, youth & summer hs ball I get all varieties of "partners". When I get
one of those guys/gals, instead if telling them they did this wrong, I ask those questions to determine if it's even worth it to share the knowledge. You can generally tell how receptive they may/may not be by their answers & tone of voice. The conversation allows you to share your experience & aspirations without throwing your resume in their face.
That's official-to-official but I'm sure it could work in a player/official-to-official situation as well.